Beta Decay

$\large \displaystyle \text{Beta decay reaction happens in two ways :}\\ \large \displaystyle \beta^{+} \text{decay: } X_Z^A \rightarrow X_{Z-1}^A + e^{+} + \nu\\ \large \displaystyle \beta^{-} \text{decay: } X_Z^A \rightarrow X_{Z+1}^A + e^{-} + \bar{\nu}.$

Assumptions:

• Z $\rightarrow$ Atomic Number.

• A $\rightarrow$ Mass Number.

Here, Atomic number changes but the Mass number remains constant. And if atomic number changes even the numbers of protons and electrons changes. So, one thing that remains constant is $\color{#3D99F6}{\text{Mass }}\color{#20A900}{\text{Number}}.$

In beta decay, a neutron is converted to a proton and an electron. The atomic number will increase by one, and the neutron to proton ratio will change since the number of neutrons has decreased and the number of protons has increased. The mass number will remain constant, because the mass number is based on the total number of nucleons (protons + neutrons), and the total number of nucleons is constant, even though the identity of the element has changed.

I firmly believe that the mass number (A) which is the sum of protons and neutrons changes slightly. mn>mp They have different masses. If I am mistaken please correct me.